Solve for $n$ : $29 + n = 9$
Subtract $29$ from both sides: $ \begin{eqnarray} \\ 29 + n &=& 9 \\ \\ {-29} && {-29} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{29 + n} &\hphantom{=}& \hphantom{9} \\ n &=& 9 {- 29} \\ \end{eqnarray} $ Simplify. $ n = -20$